A known type of apparatus for controlling dye exhaustion in a textile dyeing bath or vat is described in U.S. Pat. Nos. 3,890,510 and 4,015,134 assigned to the same Assignee as this application. In such apparatus the absorption of a color component is controlled by regulating the temperature dependent on the transparency of the dyeing fluid.
Factors influencing the evenness of dyeings in a bath dyeing operation of this type are:
The temperature/time program,
dye formula,
liquor characteristics such as the pH value,
liquor circulation,
textile material characteristics such as type of fibre etc.
With hitherto employed dyeing methods these factors had to be balanced out with each other to such an extent that the limit value dyeing rate was achieved with time-dependent linear exhaustion of the dye on the fibres with as good as possible approximation.